Field
The disclosed embodiments relate to the techniques for monitoring the capacity of a rechargeable battery. More specifically, the disclosed embodiments relate to a system for tracking the capacity of a rechargeable battery in a portable device that is plugged in to a wall adapter for extended periods of time.
Related Art
Rechargeable lithium batteries, such as lithium-ion or lithium-polymer batteries, are presently used to power a wide variety of portable electronic devices, including laptop computers, tablet computers, smartphones and digital music players. As lithium batteries age, the battery cells lose capacity regardless of whether they are being used or not. It is important to be able to track this change in capacity so the electronic device can indicate accurately to the user how much battery life remains.
Existing techniques for tracking age-related fading of battery capacity rely on the user to exercise their battery through different states of charge. For users who only use their battery sporadically, this becomes an issue when they decide to unplug their system and use it on battery power for an extended period of time. A common scenario is a user who leaves her system plugged in at her desk most of the time, but occasionally unplugs her system and uses it while travelling, for example on an airplane. In this example, if the battery ages significantly while the system is plugged in, the system will not be able to accurately estimate remaining battery life, and may erroneously indicate that battery life remains when in fact the charge in the battery is so depleted that no useful battery life remains.
Hence, what is needed is a technique for tracking the loss of battery capacity in a system that remains plugged in most of the time.